This invention relates to a pressure roller stand with adjustable drive for forcible longitudinal displacement of a drum, such as a large rotary kiln, rotating on raceways.
Large drums, as for mixing, preheating, and cooling of bulk materials, are often rotated on two or more external, circumferential raceways, each supported on two bearing rollers. Mechanical stresses in the area of linear contact between each of the bearing rollers and the raceway lateral surfaces can be very high, wearing the raceways very rapdily and reducing outputs and service lives. To decrease the high wear rates of such raceways, it is known to construct the contact surface of the raceways broader than the bearing surfaces of the bearing rollers, and to move the rotary drum during operation forcibly to and fro in its longitudinal direction across the bearing rollers.
In the German Pat. No. 897,970 an apparatus is described for the longitudinal movement of a rotary kiln supported through raceways on bearing rollers, wherein the pressure rollers controlling the longitudinal movement are positioned eccentrically on a shaft pin, so that a gear driving the shaft pin displaces the pressure roller and thereby the rotary kiln.
German Laid Open Specification No. 1,962,678 shows an apparatus to effect longitudinal movement of a rotating drum supported through raceways on bearing rollers. A pressure roller engages the raceways for longitudinal guidance of the drum, the pressure roller being supported in a pressure roller housing. The housing has three guide elements displaceable longitudinally to exert an axial force on the drum.
These structures for longitudinal movement of a rotary drum have the disadvantage that the high axial forces applied load the pressure roller housing and the pressure roller supports with appreciable bending moments. Labyrinth seals arranged between the pressure roller housing undergo appreciable uncontrollable wear, so that in a short time, for example, cement dust may penetrate into the pressure roller bearings and cause damage to the bearings and breakage of the guide elements. Furthermore, the previous pressure roller housing constructions have an appreciable space requirement, so that expensive foundation work and high-priced raceway constructions were necessary to provide free space underneath the rotary drum for pressure roller stations.
An object of the present invention is to produce a pressure roller stand with an adjustable drive for the forcible longitudinal displacement of a drum or kiln rotating on raceways, which prevents the slight operational capacitance of the construction known from the state of the art and in which by means of a flat structural construction, costly and expensive constructions of foundations and raceways may be substantially avoided.
The problem is solved according to the present invention by the pressure roller being slideable on a frame in the longitudinal direction of the drum with respect to the foundation, and an adjustable drive engaging the frame in the plane of rotation of the pressure roller. The frame and the pressure roller are advantageously integrated into a structurally flat unit, so that simple assembly of the displacement unit is afforded. Thus it is possible particularly with rotary drums of large size to increase the pressure rollers' diameter and at the same time to adapt the pressure roller frame unit according to the invention to free space between the rotary drum wall and a raceway supporting surface. In this way high costs for foundation and raceway structures may be appreciably decreased.
The advantage of the flatly-constructed pressure roller stand is further increased by the reduced structural height of the raceways in that the axial force of moving of the drum supported by raceways on bearing rollers exerts smaller bending moments on the bearing rollers and thus the bearing rollers may be reduced in size and cost.
The pressure roller is arranged in its frame so that its plane of rotation is perpendicular to the plane of rotation of the raceways. By menas of this construction, both the axial force of the rotary drum and the displacement force of the adjustable drive take effect in the plane of the pressure roller and go through its center, so that bending moments on the pressure roller frame and the pressure roller bearings are entirely avoided and a simple and nevertheless nontorsional frame construction is allowed. In this way it is possible to maintain the seal of the pressure roller bearing with respect to the pressure roller housing so free from dust that a long lifetime of the bearing and with it a high reliability and economy of the entire installation may be attained.
Further, in accordance with the principles of this invention, the frame is slidable with respect to the foundation by means of slide rails and grooves, which are coated with a synthetic material of low coefficients of static and dynamic friction. The drive is connected between the slidable frame and the fixed foundation by means of spherical bearings which take up inaccuracies in alignment among the parts. The drive itself is conveniently a hydraulic piston device. The frame of the pressure roller has ventilating apertures for convection or forced-air cooling, and an insulating sleeve may be provided between the drum surface and the pressure roller frame. It is also contemplated by the present invention that an annular frame may be provided in an alternate embodiment for applications for very high yields of bulk materials, where forces required for axial displacements are very high.
Further details, features, and advantages of the invention will be explained in greater detail in the following specification on the basis of diagrammatic drawings of the embodiments by way of example of a pressure roller stand according to the invention.